Does being tough on crime actually deter crime?

What’s the appropriate role of our prison system? Depending on
who you talk to, it’s supposed to function as punishment for
criminal activity, a deterrent to future crimes, and an opportunity
for rehabilitation. It’s often possible to find people arguing that
an existing prison system is already playing more than one of these
roles, which raises questions about how well we understand a system
that US society has committed to in a big way.

Fortunately, some researchers decided to view this question as
an opportunity and put some hard numbers to what, exactly, our
prison system is doing. Using a data set covering over 100,000
convicted criminals, the researchers compared the outcomes of
people sentenced to prison and a similar population that was given
probation instead. The results suggest that prison does limit
future violent crime by keeping criminals out of the general
population, but the experience of prison provides little deterrence
for future crime.

Violence in Michigan

A team of social scientists had access to data on everyone who
committed a felony in Michigan between 2003 and 2006. This included
followup data running through 2015, allowing the scientists to
track whether any of this population committed additional
crimes.